The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2000-272815, filed on Sep. 8, 2000, the contents of which is herein expressly incorporated by reference in its entirety.
1. Technical Field of the Invention
The present invention relates to a battery module, and more particularly to a battery module used as a battery power source for an electric vehicle.
2. Description of Related Art
FIG. 1 shows a conventional battery module disclosed in Japanese Laid-open Patent Application No. 10-106533, the battery module made by connecting a plurality of cells and coupling them integrally so as to obtain a necessary power capacity. In the conventional battery module, a plurality of cylindrical cell A shown in FIG. 2 are arranged in series in the axial direction thereof, and adjacent cells are connected together through a connector 1 shown in FIGS. 3A to 3C, by welding.
As shown in FIGS. 3A to 3C, the connector 1 is formed like a circular dish having two steps in a depth direction. An opening 17 is concentrically formed in a bottom plate 5 of the connector 1, the opening 17 for inserting a protruding portion 14 of an electrode 10 of the cell A therethrough. As shown in FIG. 4, four projections 2 formed on the bottom plate 5 of the connector 1 are welded to the electrode 10 of the cell A. Subsequently, four projections 3 formed on a cylindrical wall 4 of the connector 1 are welded to a cell case 11 of another cell A, thereby connecting the cells electrically and mechanically together.
Another conventional battery module is disclosed in Japanese Laid-open Patent Application No. 10-112299. As shown in FIG. 5 and FIG. 6, the battery module includes a tube body 21, a plurality of elements for electromotive force (i.e., unit cells). 25a, 25b, and 25c fitted on the peripheral surface of the body 21, and a case 22 for covering them. In other words, the battery module is made by accommodating a plurality of elements for electromotive force in a single case.
Furthermore, Japanese Laid-open Patent Application. No. 8-329971 discloses another battery module. As shown in FIG. 7, the battery module includes a plurality of sealed elements for electromotive force 31, a single case 36 for accommodating the elements 31, and a connector 35 for connecting the elements 31.
However, the conventional battery modules have some disadvantages. The battery module disclosed in Japanese Laid-open Patent Application No. 10-106533 necessitates a number of connectors. Moreover, it is difficult to ensure a desired mechanical strength of the battery module, since the battery module is made by connecting a plurality of cells. Furthermore, the connectors are exposed in an external atmosphere, so that they may be progressively subjected to corrosion when condensation occurs thereon due to sudden changes in environmental temperature.
Regarding the battery module disclosed in Japanese Laid-open Patent Application No. 10-112299, it is very difficult to electrically connect between collector leads 26b, 26c and a collector lead fixing member 27c for connecting between the collector leads 26b, 26c, while reducing a dead space between them.
Furthermore, the battery module disclosed in Japanese Laid-open Patent Application No. 8-329971 has a low resistance to pressure of gas generated from the element for electromotive force, since each of the elements is sealed with a sealing sheet. What is worse, such a battery module is unsuitable for a large capacity electric discharge because a current-feeding portion is made of a thin metal plate in order to seal each of the elements.
An object of the present invention is to provide a battery module having a high mechanical strength, a high weight energy density, a high volume energy density, and a corrosion-free connection between cells.
To achieve the above object, according to the present invention, there is provided a battery module which includes a cylindrical or columnar case; a plurality of elements for electromotive force accommodated in the case, the elements being placed in series in the axial direction of the case; a partition wall for spatially isolating the elements from one another; an electric connector for connecting the elements through the partition wall; and sealing plates placed on both ends of the case. In the battery module, a desired mechanical strength is obtained because the plurality of elements for electromotive force is accommodated in a single case. Moreover, since the connecting portion between the elements for electromotive force is positioned inside the case, a corrosion-free connection between the elements is achieved and the dead space is minimized, resulting in a high weight energy density and a high volume energy density. Preferably the electric connector is loaded into the partition wall by pressing, so that the boundary face therebetween is sealed to prevent liquid or gas leakage.
These and other objects and characteristics of the present invention will become further clear from the following description with reference to the accompanying drawings.